1. Field of the Invention
This invention relates to a CAD (Computer-Aided Design) apparatus with which a large scale integrated circuit (LSI), a multi-chip module (MCM), a printed wiring board (PWB) or a like apparatus is designed interactively, and more particularly to a CAD apparatus which is improved in technique of displaying a design object.
2. Description of the Related Art
In recent years, it is demanded for an LSI, an MCM, a PWB or a like device to have parts mounted in a high density and be wired with a reduced number of signal layers in a short time. Therefore, wiring lines for an LSI, an MCM, a PWB or a like apparatus are usually designed interactively displaying a design object on a display unit using a wiring CAD apparatus such as a computer graphics system. In this instance, it is required to establish a displaying technique by which existing components, connections between the components and so forth can be identified readily to proceed with interactive processing with reduced steps of operation.
A popular displaying technique for a wiring design object in a wiring CAD apparatus such as a computer graphics system will be described below with reference to FIGS. 26 to 33.
A1. In a wiring CAD apparatus which operates interactively, a part pin which is not wired yet (such pin will be hereinafter referred to as non-wired pin) is recognized in the following manner, for example, in accordance with a flow chart (steps S81 to S85) shown in FIG. 26.
In particular, a designer (operator) will first input an "instruction to display a non-wired pin" by way of an inputting apparatus such as a keyboard, a mouse or a tablet (step S81). Consequently, the wiring CAD apparatus automatically searches a non-wired line from among wiring design data inputted prior to the inputting time of the instruction (step S82) and determines whether or not a pertinent pin, that is, a non-wired pin, remains (step S83).
When a non-wired pin remains (when the determination at step S83 is YES), in order to make clear the positional relationship between the non-wired pin and another pin to which the non-wired pin is to be wired, display data for displaying a line or the like which interconnects the non-wired pin and the connection object pin is produced (step S84). The non-wired pin is displayed on a display unit based on the display data, and the connection object pin to be paired with the non-wired pin is displayed connected by way of a suitable line (step S85). For example, as shown in FIG. 28, between a non-wired pin 100 and a connection object pin 101 to be connected to the non-wired pin 100, a broken line 102 interconnecting the pins 100 and 101 is displayed.
In this instance, the non-wired pin can be displayed in various forms including 1 a displaying form wherein, by hitting a part pin displayed on the display unit by means of a mouse pointer or a like element, a line or a like element interconnecting the thus hit part pin and a non-wired pin to be connected to the part pin by a wiring line is displayed; 2 another displaying form wherein, by hitting a part displayed on the display unit by means of a mouse pointer or a like element, lines or the like interconnecting pins of the part and a non-wired pin or pins to be connected to the pins are displayed; and 3 a further form wherein, by operating a function key or a like element on an inputting apparatus or the like, lines or the like interconnecting all non-wired pins in an entire wiring design object at present and all part pins to be connected to the non-wired pins are displayed.
A2. Further, in a wiring CAD apparatus which operates interactively, a wiring pattern which is not connected to any element (such wiring pattern will be hereinafter referred to as non-connected pattern) or an end portion of such non-connected pattern is recognized in the following manner, for example, in accordance with a flow chart (steps S86 to S90) shown in FIG. 27. It is to be noted that such a non-connected pattern as described above appears, for example, in such a case that, after two part pins are connected to each other once, the opposite end portions of the wiring pattern are deleted by deletion processing or the like.
Referring to FIG. 27, a designer will observe a screen displayed on the display unit at present and, taking notice of an arbitrary region of a wiring design object on the display unit, operate the inputting apparatus so as to display the region in an increased scale (step S86). Then, the designer will observe the region displayed in the increased scale on the display unit to visually search a pertinent non-connected pattern (step S87) and visually discern whether or not a pertinent non-connected pattern is present (step S88).
If no pertinent non-connected pattern is present in the region displayed on the display unit (when the determination at step S88 is NO), the designer will operate the inputting apparatus to scroll the screen so that another region of the wiring design object is displayed on the display unit (step S89), and perform similar operations to those at steps S87 and S88 described above.
In contrast, when it is determined at step S88 that a pertinent non-connected pattern is present (when the determination at step S88 is YES), the designer will perform next processing such as to delete the non-connected pattern or connect the non-connected pattern to a predetermined part pin (step S90).
It is to be noted that, although the software for automatically searching such a non-connected pattern as described above has conventionally been developed, according to the software, a result of automatic searching is outputted merely as coordinate information of non-connected patterns in the form of a list, and the non-connected patterns thus searched out cannot be discriminated immediately.
A3. Further, in a wiring CAD apparatus which operates interactively, a wiring pattern which has a non-wired interval (such wiring pattern will be hereinafter referred to as non-wired pattern; a wiring pattern which is connected at an end thereof to a part pin but is not connected at the other end thereof) or an end portion of such non-wired pattern is recognized in the following manner, for example, in accordance with the procedure according to the flow chart (steps S81 to S85) shown in FIG. 26 described above and another flow chart (steps S91 to S95) shown in FIG. 29 which will be described below.
That a non-wired pattern is present signifies that such a non-wired pin as described above is present, and accordingly, after a non-wired pin is searched out and displayed in accordance with the procedure described hereinabove with reference to FIG. 26, the non-wired pattern is visually searched on the display unit in accordance with the procedure illustrated in FIG. 29.
In particular, a designer will input an "instruction to display a non-wired pattern" by way of the inputting apparatus (step S81). Consequently, a non-wired pattern is automatically searched based on wiring design data obtained up to the inputting point of time of the instruction (step S82) and it is determined whether or not a non-wired pin is present (step S83) as described above. If a non-wired pin is present, then such non-wired pin 100 and a connection object pin 101 are displayed connected to each other by way of a broken line (steps S84 and S85).
After a non-wired pin is searched out and displayed as described above, the designer will observe the screen (for example, FIG. 28) which displays the non-wired pin on the display unit, and taking the broken line 102 and so forth into consideration, take notice of an arbitrary region of the wiring design object and operate the inputting apparatus so as to display the region in an increased scale (step S91). Then, the designer will observe the region displayed in the increased scale on the display unit to visually search a pertinent non-wired pattern (step S92) and visually discern whether or not a pertinent wiring pattern is present (step S93).
When no pertinent non-wired pattern is present in the region displayed on the display unit (when the determination at step S93 is NO), the designer will operate the inputting apparatus so as to scroll the screen so that another region of the wiring design object on the display unit (step S94), and then perform similar processing to that at steps S91 and S92 described above.
On the contrary if it is determined at step S93 that a pertinent non-wired pattern is present (when the determination is YES), the designer will perform next processing such as to connect the non-wired pattern to a predetermined part pin (step S95).
Now, a detailed example of searching processing for a non-wired pattern will be described with reference to FIG. 28. It is assumed that, as shown in FIG. 28, the non-wired pin 100 and the connection object pin 101 are displayed connected to each other by way of the broken line 102 and the designer first tries to display the region defined by a rectangular frame 104A, which includes the non-wired pin 100, in an increased scale.
In this instance, the designer will move the displaying screen on the display unit along the broken line 102 until the region in another rectangular frame 104B is displayed in an enlarged scale, and thereupon, the designer will visually discern the pin 101 which is an object of connection of the non-wired pin 100. Thereafter, the designer will visually trace a wiring pattern 103 connected to the pin 101 to visually discern that the wiring pattern 103 is a non-wired pattern. The designer can further move the displaying screen and, at a point of time when the region in a further rectangular frame 104C is displayed in an enlarged scale, confirm the position of an end 103a of the non-wired pattern 103.
A4. On the other hand, when wiring patterns in a plurality of layers are displayed at a time on a display unit of a wiring CAD apparatus, the different layers are displayed in different displaying colors. As shown in FIG. 30, wiring patterns 105 of a first layer (L1) are displayed, for example, in blue (screened displaying portion in FIG. 30); wiring patterns 106 of a second layer (L2) are displayed, for example, in red (in FIG. 30, indicated by slanting lines); and a further wiring pattern 107 of a third layer (L3) is displayed, for example, in yellow (in FIG. 30, indicated in blank).
In this instance, the wiring patterns 105 to 107 of the different layers are displayed successively in an overlapping relationship from the uppermost layer (or lowermost layer) toward the lower layers (or upper layers).
Accordingly, in the example shown in FIG. 30, the wiring patterns 105 of the first layer are displayed uppermost (on the nearest side), and the wiring patterns 106 of the second layer are displayed under the wiring patterns 105 of the first layer. Further, the wiring pattern 107 of the third layer is displayed under the wiring patterns 106 of the second layer 106. Thus, where wiring patterns of different layers are present in an overlapping relationship with each other, the wiring layer of an uppermost layer is displayed preferentially.
Further, in another example shown in FIG. 31(a), wiring patterns 105A to 105D of a first layer are displayed, and another wiring pattern 106A of a second layer is displayed under the wiring patterns 105A to 105D of the first layer. The wiring pattern 106A of the second layer is overlapped partially with the wiring pattern 105B of the first layer and is connected to the wiring pattern 105D of the first layer by way of a via hole (or IVH (Interstitial Via Hole)) 109.
As seen in FIG. 31(a), the via hole (or IVH) 109 which extends between the different layers is displayed as a single graphic form on the display unit. Further, in order for the wiring pattern 106A of the second layer, which cannot be observed due to the presence of the wiring patterns 105A to 105D of the first layer, to be visually discerned on the display unit, a designer conventionally operates an inputting apparatus to erase the displays of the wiring patterns 105A to 105D of the first layer so that the wiring pattern 106A of the lower layer is displayed in the uppermost layer as seen, for example, from FIG. 31(a).
It is to be noted that each of rectangular portions each denoted at 108 in FIGS. 30 and 31(a) is a region called pad. The pads 108 are provided on a chip for an integrated circuit or semiconductor elements such transistors so as to allow wiring from the outside to the chip.
Meanwhile, the IVH (Interstitial Via Hole) mentioned hereinabove is a generic term for blind via holes formed only in an outer layer material of a multi-layer printed wiring board and inner via holes formed only in an inner layer material, and is a plated through-hole which interconnects two or more conductor layers of a multi-layer printed wiring board but does not extend through the printed wiring board, different from a via hole. By connecting only necessary layers to each other by way of such IVH, the degree of freedom in designing and the mounting density can be raised.
A5. In the meantime, when it is attempted to perform a wiring operation on a display unit of a wiring CAD apparatus, if a start point 110 from which wiring is to be started is designated by hitting it by means of a mouse pointer (or cursor) 111 as seen in FIG. 32, then a rubber band 112 is continuously displayed between the start point 110 and the mouse pointer 111 and consequently the positional relationship between the start point 110 and the mouse pointer 111 is continuously indicated clearly until after an end point (not shown) of the wiring line is designated by hitting it by means of the mouse pointer 111.
After the start point and the end point of a wiring interval are designated in such a manner as described above, wiring processing of the wiring interval is executed in the wiring CAD apparatus. However, if actual wiring processing reveals that wiring cannot be performed actually for the wiring interval because of presence of some obstacle or from some other cause, then an error message or the like is displayed on the display unit to inform the designer of it. The designer thus observes the error message and takes a suitable countermeasure so as to make it possible to perform wiring of the wiring interval.
It is to be noted that the obstacle mentioned above may be, for example, a location which looks on the display unit as if a wiring pattern can be disposed there but at which a wiring pattern cannot be disposed actually because more than an allowable number of wiring patterns pass there.
A6. Further, when it is tried to perform an operation of deleting a pattern wired once on the display unit of the wiring CAD apparatus, for example, a deletion start point 113 and a deletion end point 114 on a wiring pattern 115 as an object for deletion are designated by hitting them by means of a mouse pointer or cursor as seen in FIG. 33. In this instance, in order to clearly indicate the positions of the deletion start point 113 and the deletion end point 114 on the display unit, such a mark as "x" is displayed at each of the deletion start point 113 and the deletion end point 114 simultaneously upon designation of the points 113 and 114, respectively.
However, the existing techniques described hereinabove in the items A1 to A6 have such subjects to be solved as described in items B1 to B6 below, respectively.
B1. When a non-wired pin is searched, in the displaying form 1 or 2 described hereinabove wherein a non-wired pin is displayed for each part pin or each part, a designer must operate the inputting apparatus to input an instruction and must perform such processing as described above with reference to FIG. 26 repetitively by a number of times. Accordingly, a very long time is required for the operation. Further, since a non-wired pin is not displayed if such an instruction as described above is not inputted, there is the possibility that, while a non-wired pin remains, the wiring designing may be completed.
Meanwhile, in the displaying form 3 described hereinabove, since lines or the like which interconnect all non-wired pins in the entire wiring design object and all part pins to be connected to the non-wired pins are displayed simultaneously on the display unit, they make the displaying screen so complicated that the individual non-wired pins cannot still be conformed. Also in this instance, there is the possibility that the wiring designing may be completed while a non-wired pin remains.
B2. When a non-connected pattern is searched, since such processing as to take notice of an arbitrary region and search a non-connected pattern by visual discernment by the designer must be repeated, a very long time is required for the searching operation, and there is the possibility that the wiring designing may be completed while a non-connected pattern remains. Particularly, a non-connected pattern sometimes remains as a fraction, and in such an instance, it is very difficult to search out the non-connected pattern from a wiring design object of a large area.
B3. When a non-wired pattern is searched, a non-wired pin is first searched in accordance with the procedure described hereinabove with reference to FIG. 26 and displayed in such a manner as shown in FIG. 28, and then, while the display of the broken line 102 or the like on the display unit is observed, the positions of the non-wired pattern 103 and the end 103a of the non-wired pattern 103 must be searched as described hereinabove with reference to FIG. 29. Thus, a very long time is required for the searching operation.
B4. Further, in the existing displaying techniques described hereinabove, since wiring patterns of a plurality of layers and via holes or IVHs which extend through a plurality of layers are displayed successively in an overlapping relationship from the uppermost layer (or lowermost layer) toward the lower (or upper) layers as shown in FIGS. 30 and 31(a), where such a visual obstacle as a pad 108 is displayed on the first (uppermost or surface) layer, it makes it very difficult to recognize wiring patterns in the other layers (lower layers).
Particularly, where a plurality of wiring patterns are present at the same position but in different layers as seen in FIG. 31(a), the wiring patterns are displayed in an overlapping relationship with each other, and consequently, only the wiring pattern (105B) in the uppermost layer is displayed on the screen. Accordingly, it is difficult to identify the conditions of the wiring patterns in the other layers at a moment. Also it is difficult to identify at a moment from which layer to which layer a via hole or IVH (refer to reference numeral 109), which extends across a plurality of layers, extends.
Therefore, also it has been a common practice to designate a displaying layer and delete the display or displays of an upper layer or layers, for example, in such a manner as shown in FIG. 31(b) so as to provide displays for the individual layers to facilitate recognition. However, such operation is very complicated and cumbersome. Besides, if the display of an upper layer is deleted, this makes it impossible to grasp the association with a lower layer or layers immediately, resulting in deterioration in efficiency in wiring designing.
B5. Upon wiring operation, as shown, for example, in FIG. 32, the rubber band 112 is displayed extending from the start point 110 to the mouse pointer (or cursor) 111. In this instance, however, if only the region in the rectangular frame 116 is displayed on the display unit and the end point of the wiring interval is present outside the rectangular frame 116, then although the mouse pointer 111 must be moved to the position of the end point, the position of the end point, that is, the direction from the mouse pointer 111 to the end point, cannot be recognized. Consequently, the positional relationship between the start point and the end point or the direction from an intermediate location of a wiring line (the position of the mouse pointer 111) to the end point must be investigated, which requires much time.
Meanwhile, since a pattern of a noticed network cannot be identified depending upon the magnification of a wiring design object on the display unit, there is the possibility that, upon T-junction processing (processing of directly connecting a new pattern in a T-shaped configuration to another pattern wired already), an end point may be designated on a pattern of a network different from the pattern whose start point 110 has been designated. In such an instance, an error message or the like is displayed on the display unit, and the designer will observe the error message or the like and perform wiring instruction again.
Further, after a start point of a wiring interval is designated, to which location a wiring line can be wired from the start point cannot be determined unless an end point is designated actually. In particular, if an error message is not displayed, upon designation of a start point and an end point, on the display unit and predetermined wiring processing is executed for the designated wiring interval, then it becomes clear at the point of time that wiring is possible. However, if an error message is displayed on the display unit when a start point and an end point are designated, then it becomes clear at the point of time that wiring is impossible for the designated wiring interval.
Then, when wiring is impossible, merely an error message is displayed on the display unit, but the indication of what or where is a location for which wiring is impossible due to an obstacle or the like is not provided conventionally. Consequently, the designer cannot recognize which portion makes wiring impossible.
Although a skilled person can recognize, on its sixth sense, a location for which wiring is impossible to some degree, since the location for which wiring is impossible is not displayed at all, after all it is a common practice to determine a location of an obstacle or the like by supposition, wire a wiring line bypassing the location and thus attempt a wiring operation while confirming that an error message is not displayed as result of the wiring. This deteriorates the wiring operation efficiency.
B6. Upon operation of deleting a wiring pattern, for example, marks are applied to the positions of the deletion start point 113 and the deletion end point 114 as shown in FIG. 33 to designate a deletion interval of the wiring pattern 115. However, where a wiring design object is complicated and is high in mounting density, the deletion end point 114 may possibly be designated on a pattern of a network different from the network whose deletion start point 113 is designated. In such an instance, an error message or the like is displayed on the display unit, and the designer will observe the error message or the like and input a deletion instruction again.